142 KANSAS ACADEMY OF SCIENCE. 
containing Dakota leaves. From this ledge the following species have been recog- 
nized: Sterculia sp., Eucalyptus dakotensis Lx., Myrica longa Lx., Salix 
proteefolia Lx., Sequoia sp., Sassafras cretaceum Newb., Sassafras 
mudget Lx. 
It is the fact of the overlapping of the Dakota leaves and the Comanche shells 
that seemingly complicates the problem of the line of separation, which, from the 
standpoint of stratigraphy alone, is sufficiently vexing. 
Professor Mudge states that he found shells and leaves in the same ledge. 
This condition has not been noticed by the writer, but there is no reason to 
doubt the correctness of the statement. The Kiowa and its synonym, the Mentor, 
are evidently deep-sea deposits. At the close of Comanche time, and especially 
in the northern part of the area, the sea bottom was probably raised nearly out 
of the water. Many islands appeared. Numerous inlets, bays, bayous and 
lagoons were formed. Neither was the elevation constant. Depressions occurred, 
and marine shells flourished in the deeper bays. South of Mentor, Saline county, 
there is a ledge of oyster shells two feet thick. In the brackish- and fresh-water 
lagoons and inlets such forms as Unio predominate. A locality five miles north 
of Salina yields only fresh- and brackish-water forms. The islands were covered 
with dicotyledonous trees. The leaves blown off by the wind or falling in the 
course of nature were washed about by the tides and currents, sometimes being 
deposited near the shore, and again being carried into deep water. As the land 
was raised more and more the marine shells gradually perished, and only brack- 
ish-water forms remained. These are occasionally found throughout the entire 
group. In the upper part of the formation, after something like 300 feet of 
strata had been deposited, the increasing number of invertebrates, as well as 
such lithological phenomena as saliferous shales and lignites, herald the sub- 
sidence of the surface preparatory to Benton sedimentation. This group con- 
tains a marine fauna quite distinct from that of the Comanche. 
As was remarked above, in the southern Kansas areas the question is con- 
siderably simplified. The Kiowa grades upward through a series of beds more 
or less transitional in character into the true leaf-bearing Dakota. As far as 
known, the thickness of the strata, from the upper layer yielding invertebrates to 
to the lowest sandstone containing leaves, is nearly 100 feet. Doctor Ward 
rightly considers these transition beds the true base of the Dakota group. This 
would be equally true of the central Kansas region. The fact of the overlapping 
of the fossils may be considered accidental, or rather incidental, depending on 
the peculiar conditions surrounding the deposition of the material. 
In view of these facts, it does not seem either necessary, expedient, or possible, 
in the present state of our knowledge, to fix an arbitrary line of separation be- 
tween the Comanche and the Dakota. The conditions, as outlined above, are 
such that such an attempt at a fixed demarkation limit is at least impracticable. 
Taking Meek and Hayden’s classic section as a criterion, the base of the Dakota 
would probably be placed at the lowest sandstone ledge. The invertebrate pale- 
ontologist might be tempted to squeeze the Dakota into the narrow limits be- 
tween the shell-bearing horizons, the one at the base and the other in the upper 
part of the group; and, on the discovery of shell beds throughout the formation, 
to draw a line near the middle of the group, and, calling all below this line Co- 
manche and all above Benton, to eliminate the Dakota entirely. The vertebrate 
paleontologist would probably draw the upper limit of the Comanche at the 
highest stratum yielding vertebrate remains. The phytopaleontologist may per- 
haps be pardoned for insisting that the lines of demarkation of a group charac- 
terized almost exclusively by plant fossils be determined by the same criteria. 
